Personal media broadcasting system with output buffer

ABSTRACT

A personal media broadcasting system enables video distribution over a computer network and allows a user to view and control media sources over a computer network from a remote location. A personal broadcaster receives an input from one or more types of media sources, digitizes and compresses the content, and streams the compressed media over a computer network to a media player running on any of a wide range of client devices for viewing the media. The system may allow the user to issue control commands (e.g., “channel up”) from the media player to the broadcaster, causing the source device to execute the commands. The broadcaster and the media player may employ several techniques for buffering, transmitting, and viewing the content to improve the user&#39;s experience.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.60/577,833, filed Jun. 7, 2004, which is incorporated by reference inits entirety. This application is also related to co-pending U.S.application Ser. No. 11/147,664 entitled, “Personal Media BroadcastingSystem,” to Krikorian et al., filed Jun. 7, 2005, and co-pending U.S.application Ser. No. 11/147,985 entitled, “Fast-Start Streaming andBuffering of Streaming Content for Personal Media Player,” to Krikorianet al., filed Jun. 7, 2005, each of which is incorporated by referencein its entirety.

BACKGROUND

1. Field of the Invention

This invention relates generally to personal streaming mediabroadcasters, and in particular to streaming media from a media sourceinput to a client device over a network.

2. Background of the Invention

While people spend a great deal of time watching television programmingand other forms of audio-visual (A/V) content, they are also spending anincreasing amount of time interfacing with computing devices such aspersonal computers, personal digital assistants, mobile phones,dedicated multimedia devices, and other devices that, like thetraditional television, include a display. These types of computingdevices allow people to be increasingly mobile, but this mobilityreduces the time people spend at home in front of their televisions. Itwould therefore be beneficial to enable people to enjoy their televisionprogramming and other forms of A/V content they now receive at home onthese computing devices as well, regardless of location and withoutdependence on physical connections.

This ability would enable several desirable applications. For example, auser might want to access and control television and other regularlyconsumed A/V content from a personal computer (desktop as well asnotebook computers) or other computing devices around the home via theuser's local network in the home. Since cable, satellite, and othersources of television content typically enter the house at a fewdiscrete locations, allowing access to the content over a home networkgives the user more freedom to enjoy the content throughout the home.Another possible application would be to enable a user to access andcontrol television and other A/V content from any number of remotenetworks where a broadband connection is available to the user (e.g., atan airport, at work, at school, in a hotel, in a cafe, at anacquaintance's house). Yet another application would be to enable a userto access and control television and other A/V content from a mobilephone or other computing devices that can be connected to a wide areanetwork (e.g., GPRS, W-CDMA, CDMA-2000, 1XRTT, 1XEVDO, and the like). Invarious applications, users are likely to want to access their mediacontent stored on devices, such as personal computers and other deviceshaving storage, from remote networks. Nevertheless, network bandwidthand other limitations have made it difficult to provide an effective andenjoyable remote media experience for the user.

But traditional streaming media solutions do not enable theseapplications in any effective way; moreover, they suffer from technicallimitations that would prevent their use in personal media broadcastingapplications like those described above. Accordingly, it would bedesirable to enable users to access their A/V content from any of avariety of remote locations inside or outside the home, as such contentis currently available only from locations in the home thattraditionally receive and play it (e.g., a television set).

SUMMARY OF THE INVENTION

A personal media broadcasting system enables video transmission over acomputer network, allowing a user to view and control media sources overa computer network from a remote location. In one embodiment, thepersonal media broadcasting system includes a personal media broadcasterand a media player. The personal media broadcaster may be configured toreceive as an input virtually any media source. The broadcasterdigitizes and compresses the received media content (if necessary), andstreams the media over a computer network to the media player. The mediaplayer may reside on any of a wide range of client devices for viewingthe media. A user may send control commands (e.g., “channel up”) usingthe media player back over the network to be executed by the mediasource device, thus affecting the media stream received by the mediaplayer.

In one embodiment, a personal media broadcasting system includes apersonal media broadcaster and media player client, which communicatewith each other over a network. The personal media broadcaster canaccept an A/V signal from one or more A/V source devices. From this A/Vsignal, the personal media broadcaster constructs a media stream that issuitable for transmission over a network to the media player client. Thepersonal media broadcaster includes a network interface for transmittingthe media stream to the media player client. As the media stream isreceived at the client, it can be viewed by a user using the mediaplayer client. In one embodiment, the personal media broadcaster is adedicated appliance, not a general purpose computer. In this way, ageneral purpose computer need not be powered on and connected to the A/Vsource devices for the user to receive media content remotely. Inanother embodiment, the media player client can run on any general ormulti-purpose device (such as a personal computer or cellular phone),beneficially avoiding the need for the user to carry special equipmentto use the broadcasting system. The computer network over which thebroadcaster and media player client communicate may comprise a wide areanetwork, such as the Internet, allowing the user to receive mediacontent from the home to anywhere in the world where a connection to thenetwork is available.

To improve the user's experience, the person media broadcasting systemmay employ any of a number of techniques for buffering, transmitting,and viewing the content. In one embodiment, for example, the mediastream is constructed by encoding the audio/visual signal using a bitrate selected at least in part based on an amount of free spaceremaining in an intermediate output buffer used to temporarily store themedia stream before it is transmitted to the media player client. Whilevarious measures of occupancy of the intermediate output buffer can beused, one involves the use of multiple watermarks to measure the freespace available in the buffer. The encoding bit rate can be decreasedeach time the free space dips below a watermark, while it can beincreased when the free space rises above a watermark or if the freespace never drops below the watermark in the first place. In this way,the encoding bit rate can be dynamically adjusted based on currentperformance of the system, and this dynamic adjustment can occur at thebroadcaster without requiring feedback from the client.

In another embodiment, the media player client implements a fast-startmechanism by which the media player receives a media stream in real timefrom the personal media broadcaster and stores the media stream in abuffer. The media player client plays the received media stream from thebuffer at a decreased playback speed without waiting for the buffer tofill to a predetermined threshold. While the playback speed is kept at aslower rate than the streaming media content is received, the bufferfills (albeit at a rate slower than the media stream is received). Thisallows the media player client to play a received media stream withoutwaiting for its buffer to fills, which improves the user's experiencedramatically in situations such as where the user is changing channelsor operating a menu on the remote A/V source device. In addition, themedia player client may further enhance this experience by switchinginto a control mode when the client receives a user command to controlcontent in the media stream. When the client enters the control mode,the buffer is flushed and the received media stream is played. In thisway, the content in the buffer need not be displayed on the clientdevice, and the user can then almost immediately receive visual feedbackconfirming the user's command to control content in the media stream.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a media broadcasting system, in accordancewith an embodiment of the invention.

FIG. 2 is a block diagram of a set of input and output connections for apersonal media broadcaster, in accordance with an embodiment of theinvention.

FIG. 3 is a block diagram of a personal media broadcaster, in accordancewith an embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Overview

Embodiments of the invention allow for distribution of A/V content froma variety of A/V source devices over a computer network to a clientdevice. As used herein, A/V content may include any type of mediacontent, including audio or video content, or both. In one embodiment, apersonal media broadcaster takes as an input an audio or video signal,digitizes and compresses the content (e.g., in Windows Media Video,MPEG-4, or H.264), and streams the content over an IP network (such asIP4 or IP6) to a client device for viewing and/or listening to thecontent. The personal broadcaster, which may be implemented as anembedded solution, may allow the user to issue control commands, such as“channel up” via an IR or serial command, back over the network to beexecuted by the original source device. Using various embodiments of thepresent invention, a user can connect to the personal broadcaster acable or satellite set-top box, a personal video recorder, a DVD player,a DVD jukebox, a music server, a satellite radio receiver, a camcorder,a digital video recorder (DVR) or any other A/V source component. Thisway, the user can view and control the live output of these sources fromany networked device. Various embodiments of the present invention mayinclude different components, including a personal broadcaster and mediaplayer. The media player may be a software application that runs on aclient device, which is configured to receive the media stream createdby the personal broadcaster. Different client software applications canexist for different classes of client devices, such as personalcomputers and cell phones. The client may be able to connect to thepersonal broadcaster through a Web browser interface.

The system described herein may be applied in a number of applicationsor usage scenarios. For example, there are a variety of uses in the homeover a wired or wireless home network for the system. In the home, userscan view and control their A/V source components, such as a personalvideo recorder (PVR) or a cable set-top box, from any desktop PC,notebook PC, PDA, or other network devices. For example, thisapplication allows a user to convert a wireless notebook PC situated inthe kitchen into a wireless LCD TV. As another example of in-home use,young parents can pair a personal broadcaster with a simple analogcamera and place them in the baby's room to provide a real time videoand audio stream of their child displayed on a device in anotherlocation in the home.

Another usage scenario category relates to users who are away from homebut have access to a broadband connection. This access can be in avariety of locations, such as at work, at school, at a friend's house,in a cafe, at the airport or in a plane, or in a hotel. From theselocations, users can connect to their personal broadcaster over thepublic Internet and enjoy the same live television experience that theyhave at home. The present invention allows users that are away from hometo access the full breadth of programming they are accustomed to, andeven view content that they previously captured on their personal videorecorder.

Yet another usage scenario category relates to individuals with mobilephones, communicators, or other wide area network devices. On emergingnetworks, the bit rate is now high enough for users to enjoy streamingvideo on their devices. This opens up new possibilities for the personalbroadcaster to deliver a wealth of programming to the mobile user, allof which originates from the user's own home.

The media stream transmitted from the personal media broadcaster to themedia player client networks can take advantage of a combination of anynumber of networking protocols, including HTTP over TCP/IP, as well asUDP, RTSP, RTP, RSVP, and the like. Because embodiments of the inventioncan accept, digitize, encode, and stream any analog A/V source, thereare a vast number of uses for the personal broadcaster—from a securitycamera system to a method for extending a user's satellite radio to theuser's cell phone.

System Architecture

FIG. 1 is a block diagram of the media broadcasting system in accordancewith one embodiment of the invention. As illustrated, a personal mediabroadcaster 100 is configured to receive an input video signal from awide variety of A/V source devices 120. For example, any component ordevice having analog A/V outputs can be connected to the personalbroadcaster 100. Upon receiving the video and/or audio feed from aconnected A/V source device 120, the personal broadcaster digitizes,encodes, and streams the digitally compressed media to the home Internetgateway 110. The gateway 110 may comprise one or more separate devices,including a router, a switch or hub, and/or an analog, DSL, cable orother type of broadband modem, or the gateway 110 may comprise a singledevice that encompasses one or more of these functions.

The gateway 110 may be coupled to a local area network (LAN) 140 thatcouples several computing devices in a user's home. According to knowntechniques, any number of local clients 150 may be able to communicatewith the home Internet gateway 110. In this way, created by the mediabroadcaster 100 may be routed to any of these local clients 150 by wayof the local network 140, either through the gateway 110 or directly.The local area network 140 can be wired or wireless, as the presentinvention is not limited to any particular network technology orconfiguration. The local clients 140 can be any number of device types,including but not limited to desktop and notebook PCs, Web tablets,PDAs, embedded clients built expressly for the purposes of decoding thestreams of the personal broadcaster, and other devices capable ofreceiving and/or playing a media stream over a network.

The media streams created by the personal broadcaster 100 may also bereceived by remote clients 170 from a remote network 160. The remotenetwork 160 may comprise any suitable networking technology, includingbut not limited to wide area mobile networks (e.g., GPRS, EDGE, 1X-RTT,1x-EvDO, and FOMA 2.5G and 3G cellular networks), WiFi and other publicbroadband access locations, WiMAX networks, other LANs (such as at work,school, or a friend's home), and direct connections to other Internetservice providers. As with the local clients 150, the remote clients 170may include any number of device types, but not limited to desktop andnotebook PCs, Web tablets, PDAs, embedded clients built expressly forthe purposes of decoding the streams of the personal broadcaster, andother devices capable of receiving and/or playing a media stream over anetwork.

In one embodiment, the local clients 150 and/or the remote clients 170execute a client software application that includes a user interface forrequesting content from the broadcaster 100 and for viewing thatcontent. In another embodiment, the client functionality is provided bya Web site and is accessible by the local clients 150 and/or the remoteclients 170 via a Web browser. When a remote client 170 wishes toconnect to the stream of the personal broadcaster 100 using the clientapplication or via a Web browser interface, it may specify the home IPaddress of the user to access and pull the media stream from thepersonal broadcaster. This action sends a request to the personalbroadcaster, and the request travels across the public Internet, to thenetwork of the user's Internet service provider (ISP), into the home viathe telephony or cable infrastructure (or wirelessly in the case of thefixed wireless or satellite broadband ISP), to the home Internet gateway110, and finally to the personal broadcaster 100.

In one embodiment, a central server 180 is coupled to the remote network160 and provides one or more roles, including that of DNS server.Because most residential ISPs allocate dynamic IP addresses via DHCP, asopposed to providing static IP addresses, there is a need for a systemthat provides a consistent method for accessing the user's home networkfrom remote networks. In the embodiment illustrated in FIG. 1, thecentral server 180 assigns the personal media broadcaster 100 a DNS name(e.g., username.slingbox.com) and correlates that DNS name to the user'sIP address. To account for the dynamic nature of the IP address, in oneembodiment, a dynamic DNS client application resides on the personalbroadcaster 100. The dynamic DNS client application reports to thecentral server 180 any change to the IP address leased by the ISP. Whena remote client 170 needs to communicate with the broadcaster 100, theclient 170 first obtains the associated IP address from the centralserver 180. In this way, the DNS address called by a user on a remoteclient 170 is the current IP address of the gateway 110, even when thataddress changes over time.

To make this process even easier for the user, so that the user need notmanage a constantly changing IP address or enter a DNS name, much of theprocess for connecting to a personal broadcaster 100 can be abstractedfrom the user. For example, in one embodiment, the user need only toenter the name of the personal broadcaster, or select an iconrepresenting the personal broadcaster, and then enter the correspondingpassword before being automatically directed to their personalbroadcaster 100. This can be accomplished by tying a unique device nameto the DNS name assigned to the user's dynamic IP address. Thetranslation between the device user name and the DNS name can take placewithin the remote client 170 itself, or it can be accomplished through adirectory maintained on the central server 180.

Connections from a local client 140 or a remote client 170 can beaccomplished either by using a client application designed specificallyfor the purpose of accessing the personal broadcaster stream or via atraditional Web browser. The option of using a Web browser provides forwide range of client compatibility without the need for configuration,while the client application provides for an optimized experience. Theclient application or the Web interface may prompt the user for apassword before allowing communication with the broadcaster 100, as asecurity measure. As an additional measure of security, the media streamcan be encrypted.

In one embodiment of the invention, there is a limit of one connectedclient (applies equally to remote clients and local clients) per device.That is, only one client at a given point in time can be connected toand streaming from the personal broadcaster. Other variations of thisembodiment can provide for multiple simultaneous sessions. Still othervariations can allow for multiple simultaneous sessions from localclients, but maintain a single session limit for remote clients.

FIG. 2 illustrates an embodiment of the personal media broadcaster 100having an interface for receiving a video signal from a collection ofpossible A/V source devices 120. The personal broadcaster 100 can thussupport a number of input types and possibly may include a number ofoutputs types, according to one embodiment of the present invention. Inthe embodiment illustrated in FIG. 2, the personal broadcaster 100 cansupport a composite video input 210, an S-video video input 200, acoaxial cable input 250, and left and right audio inputs 220. Thepersonal broadcaster 100 may also have a coaxial cable output 260, wherethe input cable signal is split inside the personal broadcaster 100 toallow a pass through of that signal for local viewing. Pass-throughoutputs for A/V, S-video, and any of the other inputs may also beprovided for the same purpose. A wide variety of video and audio inputsare possible, in addition to those shown in FIG. 2. Inputs and outputscan be either analog (e.g., component video) or digital (e.g., DVI, IEEE1394, USB, SDI, Toslink optical, or composite coax digital audio), andthere may be multiple connectors of a single type.

FIG. 2 also includes an IR output 270 and/or an RS-232 output 280. Theseoutputs are intended to provide the final leg of backchannel controlthat originates from the client device. Depending on whether the A/Vsource device 120 is controlled via IR or serial commands, the userconnects an emitter cable from the appropriate output on the personalbroadcaster 100 to a serial input or the IR receiver on the A/V sourcedevice 120. This provides the communication means that allows the clientto control the A/V source device 120 (e.g., to change the channels).

In FIG. 2, the personal broadcaster also includes an Ethernet port 290that provides a communication interface to the home Internet gateway110. In some embodiments of the invention, the personal broadcaster 100also supports wireless networking (e.g., through a built-in 802.11capability), and the broadcaster 100 may even be built as an accesspoint (AP) or router for a wireless network according to a wirelessnetworking standard such as 802.11. The personal broadcaster 100 canalso include a power connector 230, a hard reset button 240, and anumber of indicator lights (e.g., on a front panel) that show the stateof the personal broadcaster 100. Many other inputs and outputs are alsopossible. For example, the personal broadcaster 100 can have video andanalog outputs for a local display and sound.

FIG. 2 also shows the connections possible between an A/V source device130 and one embodiment of the personal broadcaster 100. As illustrated,an S-video cable and left and right composite audio cables connect thepersonal broadcaster 100 and an example A/V source device 120. Becausethe A/V source device 120 in this example is controlled via IR, controlscalled for by the remote client 170 or local client 150 are relayed fromthe personal broadcaster 100 to the A/V source device 120 via an IRemitter 285 (e.g., an IR blaster assembly). One end of the IR emitter285 is plugged into the personal broadcaster 100, which “blasts”appropriate IR codes through a wire and out an IR LED of the IR emitter285. Accordingly, the IR emitter 285 is placed directly in front of theIR receiver of the A/V source device 120.

The personal broadcaster 100 connects to the home Internet gateway 110from its Ethernet port 290 (using, e.g., a Cat5 cable), which connectioncan be direct or via an Ethernet wall jack located near the personalbroadcaster 100 (which in turn connects to the home Internet gateway110). In other embodiments, the connection between the personalbroadcaster 100 and the home Internet gateway 110 is wireless, where thebroadcaster 100 may include built-in wireless or power line networkingcapability.

FIG. 3 is a block diagram showing the internal components of thepersonal media broadcaster 100, according to one embodiment of theinvention. As shown, the broadcaster 100 includes an input interface 305for receiving any of a variety of input types, including an RF signalfrom analog cable or antenna, an S-video signal, a composite videosignal, and a left/right audio signal. Because an RF signal includes anumber of video signals modulated therein, the input interface 305 iscoupled to provide the RF input to a tuner 310. The tuner 310 filtersthe RF signal for a selected channel, demodulates the channel, andconverts the signal into separate analog video and audio for furtherprocessing by an audio/video decoder 315. The input interface 305 iscoupled to provide the S-video signal, a composite video signal, and aleft/right audio signal directly to the A/V decoder 315, as thosesignals need not be processed by a tuner 310.

In one embodiment, the A/V decoder 315 converts the analog video inputinto YUV video and applies various types of filters and colorcorrections to the signal. The A/V decoder 315 also extracts verticalblanking interval (VBI) data, such as close caption, tele-text, and copyprotection bits. The A/V decoder 315 also decodes the tuner audio andconverts it into stereo or mono digital audio, depending on thebroadcast signal. The analog signal is further converted into a digitalsignal in the A/V decoder 315. The digital video and audio from the A/Vdecoder 315 is then sent to a processor 320 for further processing. Thepersonal broadcaster 100 may include memory 330, such as flash memory orSDRAM, used by the processor 320 for performing its associatedprocessing tasks. The memory 330 may also be used as a buffer for theoutgoing media stream, as described herein for various embodiments.

In one embodiment, the processor 320 performs pre-processing on thedigital audio and video before compression. The pre-processing can beperformed based on the input type, compression properties, and targetbit rate. After pre-processing, the processor compresses the audio andvideo to a desired bit rate using any suitable compression technique(such as WM9, MPEG-4, H.263, and H.264). The compressed audio and videoare multiplexed into a single media stream together along with otheruser data such as close caption, tele-text, parental control, andMacrovision. In one embodiment, the processor 320 is capable ofstatically and/or dynamically adjusting the compression bit rate, framerate, resolution, and filtering depending on a user request, the inputcontent, available network bandwidth, or on any other data known to theprocessor 320. The compressed media stream is then converted intonetwork packets for transmission over the local network 140 or a remotenetwork 160 via the network interface 325. The network interface 325 maybe a wireless or a wired interface, or may have provisions for bothtypes. As mentioned above, the personal broadcaster 100 may also receiveand process commands received from a client over the network interface325. Some examples of these commands include selecting a particularchannel, automatic scanning of channels, switching between RF input andbase-band input, changing compression properties (compression type, bitrate, frame rate, resolution, and other properties), remotelycontrolling commands for the IR blaster, and any other command that auser may desire for viewing content from the A/V source device 120.

The broadcaster 100 may further comprise a controller interface 335 forinterfacing with an output for controlling an A/V source device 120. Asmentioned above, control of an A/V source device 120 may be performedusing an RS-232 serial controller or an IR emitter 285. The controllerinterface 335 thus receives the appropriate output signals from theprocessor 320 and provides the corresponding interface for controllingan operation of an A/V source device 120.

While FIG. 3 shows an embodiment of the broadcaster 100 that only takesanalog inputs, other embodiments may accept digital inputs as well. Forexample, embodiments of the present invention can be incorporated intoservice offerings from cable MSOs or DBS providers. In these variations,the personal broadcaster can have direct access to the digital bitstream being broadcast. This can be through incorporation of thepersonal broadcaster into a set-top box or home Internet gateway by theservice provider, or through some digital interconnect such as IEEE 1394or USB 2.0. With access to the digital bit streams, digitizing andencoding/compression of the streams can be entirely unnecessary. Forthese inputs, however, the personal broadcaster can be asked totransrate or transcode the media to a bit rate that is low enough foreffective distribution across local area networks and upstream through ahome Internet gateway and out to the public Internet for connection byremote clients. In variations that include digital inputs, analog inputsand a digitization and encoding function can still be present.

Despite the specific network topology illustrated in FIG. 1, there aremany variations on the present invention that have the personalbroadcaster placed in different positions relative to the othercomponents. For example, one variation of one embodiment has thepersonal broadcaster incorporated into a home Internet gateway. Byintegrating with the router functionality, the broadcaster cancompletely automate the process of port configuration (e.g., portforwarding). Alternatively, if the home Internet gateway is actually twoor more devices (e.g., a cable modem and a stand along router/switch),the personal broadcaster can be located between the cable modem and therouter. Both of these variations of the present invention provide aunique quality of service opportunity. Because the personal broadcasteris upstream from all networked clients and can “talk” with the networkrouter, the video streams from the personal broadcaster can beprioritized ahead of other, less time-critical traffic. The control canbe applied both to traffic moving within the local area network as wellas to traffic moving out from the local area network to the Internet.For example, a video stream coming from the personal broadcaster can begranted higher priority than a print job request over the local network,or an email download from a remote POP3 server. In either case, thepersonal broadcaster preferably incorporates a network switch as part ofits architecture.

As shown in FIG. 1, the personal broadcaster 100 may also be able toreceive a digital audio or video stream or other digital media from anon-network storage device 130. The on-network storage device 130 may bea personal computer, a networked attached storage device, or a dedicatedmedia server. For example, a user could have a collection of audio andvideo clips stored on a personal computer or media server that resideson the same home network as the personal broadcaster. The user couldthen access the media on a remote client 170 over a remote network 160by logging into the personal broadcaster 100.

When wishing to stream media stored on an on-network storage device 130to a remote location, a challenge arises. The bit rate of the mediaclips present on the on-network storage device can be higher than thebit rate supported by the upstream link of the user's broadband service.For example, a video clip on an on-network storage device 130 can have abit rate of 800 kbps, whereas very few broadband connections currentlyhave an uplink speed equal to or greater than that. In such cases, thebit rate of the source media signal is reduced and its encoding formatis possibility changed. The personal broadcaster 100 may perform thistransrating and transcoding functionality. In this situation, thepersonal broadcaster 1100 acts as a networked-attached transrater andtranscoder. The broadcaster receives the media stream from theon-network storage device 130, transrates and possibility transcodes themedia, and outputs a media stream with a sufficiently low bit rate sothe media can be effectively streamed upstream from the user's broadbandservice. The method for determining the proper transrating ortranscoding settings (e.g., the bit rate to which the source content isto be reduced) can be accomplished within the framework for determiningthe throughput currently supported between the personal broadcaster andthe local or remote client, outlined below.

The use of the personal broadcaster 100 as an agent to transrate and/ortranscode the material residing on one or more on-network storagedevices 130 has the benefit of creating a system where only one device(the personal broadcaster) streams media upstream through the homeInternet gateway 110 and out to the Internet 160. This is beneficialbecause the user does not have to make further configurations to the NATor firewall of the home Internet gateway, which can include manuallyforwarding a port to allow direct access to each on-network storagedevice.

In addition to requiring further configuration, streaming contentdirectly from the on-network storage device 130 can create securityconcerns for the user, especially if the on-network storage device is aPC. Because allowing a PC to stream directly upstream to the publicInternet involves opening a port on the firewall/NAT that forwards tothe PC, a user can be concerned that other personal or privateinformation is at risk for being exposed. By relying on the personalbroadcaster to be a gateway for streaming media to the public Internet,the PC or on-network storage device on which the media is stored neednot have a port forwarded to it. In such an embodiment, the personalbroadcaster is the only device for which NAT port configuration isrequired.

In addition, using the personal broadcaster instead of the on-networkstorage device to transcode and transrate content prevents the CPU onthe on-network storage device 130 from being unnecessarily taxed. Thisis especially important if the on-network storage device 130 is a PC,because the increase in CPU utilization would detrimentally impact theperformance of the PC for accomplishing other tasks.

Because the personal broadcaster 100 provides the user with access tothe same A/V source devices 120 available at home, it makes sense toprovide the user with an interface to the A/V source device 120 similarto the one used in the living room setting. Most often, this is ahandheld remote control. In one embodiment, therefore, a “virtual”remote control is provided by the client application that includeseither a generic image representing the A/V source device's remotecontrol or an image or likeness of the actual A/V source device's remotecontrol. Moreover, the client application may support a number ofvirtual remote controls, one customized for each A/V source device 120.Interfaces on the client application are thus selected by the user toresemble each particular A/V source device 120 found in the user's home.For example, if a TiVo personal video recorder is connected to thepersonal broadcaster, the user can decide to use the TiVo skin whichmodifies the virtual remote control on the client application toresemble the TiVo remote control. Remote control commands are mapped tothe graphical image in such a way that a press of the button triggersthe action suggested by the image of the button (e.g., pressing on CH+button turns the channel from 3 to 4).

In one embodiment, the client application contains a database of remotecontrol skins from which to choose. In this case, a central databasemaintained on the central server, is likely to update the clientapplication upon configuration to ensure that the latest remote controlskins are available to the users. In addition, third parties may beallowed to create and share images with commands mapped to particularregions of the image. In this case, a method for “plugging-in” the thirdparty remote control skins is provided to the user. To allow thirdparties to create skins for the media player, an API is provided toallow access to some of the features and functionality within the mediaplayer client. Third party skins allow users to develop content as wellas third party device manufacturers and service providers to makevirtual remote controls that closely resemble the physical remotecontrol associated with an A/V source device 120. The virtual remote onthe client application can thus be made easier to use, since the user isused to its layout.

Operation of Personal Media Broadcasting System

As described above with reference to FIGS. 1 through 3, the personalmedia broadcaster 100 can receive an input video signal from any of anumber of A/V source devices 120. The broadcaster 100 then prepares thereceived video signal as a media stream for being transmitted over anetwork to a remote or local client, where the media stream is viewed bythe user. Additions, alternatives, and refinements to this generalprocess are described below.

Control of Audio/Visual Source Devices

As stated above, embodiments of the personal media broadcaster allow auser to control an A/V source device from clients connected to theremote or local networks. The client may allow for control of the user'sspecific model of A/V source device. Upon initial configuration of thepersonal broadcaster and a client, the user indicates which make andmodel of A/V source device the user would like to control (e.g., TiVoPersonal Video Recorder Series 2). The configuration software on theclient then identifies the group of IR or serial codes that correspondto the specific A/V source in question. This can be performed bysearching a database that ships with the included software, an updateddatabase residing on the central server, or a database that resides onthe personal broadcaster.

In one embodiment of the invention, the IR codes is then stored on theclient device. When a user wishes to invoke a code, the user selects thegiven command on the control panel or virtual remote control in theclient application. The client application then sends the correspondingIR or serial command over the IP network. Once the IR or serial commandreaches the personal broadcaster, the personal broadcaster processes thecode and sends it out the IR or serial output, triggering the requestedaction in the A/V source device. The connection between personalbroadcaster and the A/V source device can be an IR emitter, in the casethat the A/V source device was to be controlled via IR, or an RS-232port, in the case that the A/V source device was to be controlled byserial commands.

In another embodiment, the IR and serial codes are stored on thepersonal broadcaster rather than the clients. In this case, a clientdevice that requests a given command sends a notation representing thatcommand (e.g., “CH UP” if the user wants to change the channel from 4 to5) rather than the IR or serial control code itself. When the notationrepresenting the command reaches the personal broadcaster, the personalbroadcaster performs a simple lookup, and outputs the appropriate IR orserial code. Certain commands or selections made on the client devicecan activate a series of commands, also known as a macro. For example,by clicking on the “CNN” button (which can possibly be represented by alogo of the network), the combination of commands that tune the A/Vsource device to CNN would be triggered. For example, if CNN was channel202 on a user's DirecTV system, a press of the “CNN” button can triggerthe following commands in succession: “2,” “0,” “2,” and “Enter.”

To make the set up of multiple client devices easier, profiles of the AVsource devices used can be stored in the personal broadcaster during theconfiguration of the initial client device. This enables easyconfiguration for subsequent client devices, as the personal broadcasterinforms the subsequent client device which A/V source devices it is ableto connect to, and which IR or serial codes it uses.

Adjustment of Encoder Settings Based on Throughput and Device Capability

Because the broadcaster enables access of a media stream by a variety ofclient device types connected to the local area network as well avarious remote networks, the available data throughput present betweenthe personal broadcaster on one end and the local clients and remoteclients on another can vary considerably based on network topology.There is also likely to be considerable throughput variation in a givenconnection, due to competing traffic and general network congestion. Inone embodiment of the invention, a method for optimizing the audio(e.g., bit rate and sampling rate) and video (e.g., bit rate,resolution, and frame rate) compression based on available networkbandwidth and capabilities of client device is implemented.

Because various embodiments of the present invention encompass both thepersonal broadcaster and the client devices, and these elements canoperate in a 1:1 relationship (i.e., each broadcaster may accept onlyone client connection at a time), the two components are able to act inconcert to optimize the experience for the user. In one embodiment, theoptimization process includes an initial optimization stage and anongoing optimization stage.

In the initial optimization process, the client and personal broadcastercommunicate to mutually establish the capabilities of the client device,as well as the throughput of the connection between the personalbroadcaster and the client device. The client device first requests thepersonal broadcaster to send a set number of bits to the client (thiscan happen automatically at first connection, or can be manually orderedby the user to recalibrate initial optimization). Based on the time ittakes for the client to receive those bits, the client has an idea ofthe actual data throughput between the personal broadcaster and theclient. With this information in hand, the client instructs the personalbroadcaster to begin streaming at a rate compatible with thisthroughput. This is not likely to be the full rate of throughput, butsome rate less (for example, 80% of throughput), to allow for inevitablevariation in network bandwidth. In choosing the proper resolutionsetting, the application residing on the client notes its currentcapabilities (i.e., resolution of its display) and pairs the appropriatebit rate setting with the appropriate resolution setting in its commandto the personal broadcaster.

The client can learn of its capabilities in several ways. One can berelated to the version of the application itself. For example, theapplication for a Pocket PC can know that the device best supportsstreams at or below a certain resolution and frame rate. Another way isto take inventory of system resources before it sends the request. Forexample, the client can identify its display resolution and incorporatethis information in the streaming request to the personal broadcaster.

The initial optimization process represents a starting point that canvery well provide for the proper encoder settings. However, thevariability of network bandwidth over time calls for a system that isdynamic in nature and capable of real time changes to the encodersettings. To address this variability, one embodiment of the presentinvention implements a feedback loop between the client and personalbroadcaster to maintain the proper encoder settings over time. Thisfeedback loop can be implemented in a number of ways. In one embodimentthe client gives notification to the personal broadcaster when itexperiences frame drops. Alternatively, the client communicates, fromtime to time, the size of the buffer, or the total measured throughput.The client may communicate any or all of these statistics, or any otherdata that reflects on the need to adjust the settings.

Given this feedback from the client, the personal broadcaster alters theencoder settings. For example, the personal broadcaster can reduce theencoding bit rate from 350 kbps to 280 kbps if the size of the bufferbecomes reduced or an unacceptable number of frame drops are observed.The time between measurements and feedback received from the client canvary, and the figure depends on a balance between reacting quickly tosignificant changes and overcorrecting based on temporary blips. Basedon the feedback, the personal broadcaster can adjust the settings upward(e.g., increase encoding bit rate) as well as downward.

While one embodiment provides for a method of automatic adjustment ofencoder settings, the user may also have the ability to set the encodersettings manually. These manually adjustable settings include framerate, bit rate, resolution, “quality,” and time between key frames forvideo, bit rate and sampling rate for audio, as well as client sidesettings that can impact performance, such as buffer size and smoothing.

Adjustment of Encoder Settings Based on Programming Type

While the data throughput between the personal broadcaster and theclient may be one important determinant of the proper encoding settings,the type of content being viewed may also be an important criterion. Forexample, fast motion video from a sports program requires a higher framerate than a talk show, which features much less motion. Likewise, videowith little movement can require comparatively lower bit rates orresolution than fast motion video to achieve an acceptable quality. Thisis because video with slower movement tends to be encoded much moreefficiently. Accordingly, the encoder settings may be selected based onthe type of programming being encoded.

There are various methods for determining the type of content beingviewed, and hence the proper range of encoder settings. First, there canbe settings that apply generally to all content on a given channel. Byidentifying the programming channel or network to which the personalbroadcaster is tuned (e.g., HBO or NBC), the client can request suitableencoder settings. For example, there can be a rule that when thepersonal broadcaster is streaming content from ESPN, the frame rate isalways set at 30 frames per second. Such rules can be stored on theclient or on the central server, which informs the client of the propersettings for a requested channel. Moreover, the rules can be learnedover time by an individual's own client, which observes the settingschosen by the user for certain network programming.

In a further refinement, the encoder settings may be customized based onthe specific programming being watched. Because a major networktypically has content that is both demanding, high-motion programming(such as a major sporting event) and easy, low-motion programming (suchas a newscast), selecting encoder settings based solely on the channelmay not be efficient for many channels. Accordingly, by crossreferencing the current channel with the current time of day, the systemcan determine the program that is being viewed, and the encoder'ssettings can be selected based on the actual program being viewed.

In another embodiment, the system constantly monitors the A/V contentbeing encoded. Metrics based on pre-selected criteria (e.g., amount ofmotion in video) are generated, and this information is used to assignor adjust the encoder settings to the personal broadcaster dynamically.Alternatively, the media player may receive from the user an indicationof what kind of content is being watched (e.g., action, music, news,etc.), which is mapped to predefined profiles in the framework optimizedfor that kind of content.

Buffering and Control of Buffer Resources

In accordance with one embodiment of the invention, the personal mediabroadcaster implements a buffering scheme to manage its buffer resourceswithout requiring feedback from a client device. As mentioned above, thebroadcaster and the client may communicate using TCP as a transportprotocol, where the broadcaster acts as a server. Beneficially, TCP is areliable protocol and ensures that sent data always reaches itsdestination in the correct order. Parameters and/or behavior of the TCPstack on a server can be monitored to estimate network congestion andspeed according to one or more known techniques.

In accordance with an embodiment of the invention, a large buffer isadded between the encoder (which generates the data) and the TCP stackon the network interface (which transmits the data). This additionalbuffer layer added above the TCP stack helps to avoid loss of data dueto network congestion and the variability of data rates. In oneembodiment, with reference to FIG. 3, the encoder functionality isperformed by the processor 320, the TCP stack functionality performed bythe network interface 325, and the buffer layer implemented in thegeneral memory 330 or in a memory module dedicated for the large buffer.The size of this buffer can be selected in consideration of at least twoparameters: the minimum data that can be generated by the encoder andthe maximum network down time that has to be supported. Although thesystem cannot prevent data loss when available bandwidth goes belowminimum bandwidth required by the broadcaster for extended period oftime, a larger buffer helps to reduce this risk.

As the data for the media stream are being generated by the broadcaster,the intermediate buffer acts as a FIFO queue. When the available networkbandwidth is more than the encoder's bandwidth, the broadcaster is ableto send data as soon as it is generated. The intermediate buffer willbegin to empty. When the available network bandwidth is less than theencoder's bandwidth, the broadcaster will generate the data faster thanit can be transmitted. This will begin to fill the buffer. The buffermay therefore vary between being completely full and completely empty.To classify the occupancy of the buffer, a number of watermarks aredefined to indicate the amount of free space left in the buffer. Whilethe number of watermarks can vary, in one embodiment four watermarks areused—at the 90%, 75%, 50%, and 30% levels. As data are added to andtaken from the buffer, the amount of data filling the buffer can changeover time. When this level reaches one of the watermarks, variousactions are taken depending on which watermark has been reached.

The amount of free space left in the intermediate buffer is observed fora period of time (e.g., one minute). If the amount of free space in thebuffer remains above the 90% watermark during the last observationperiod, the encoder's output bit rate may be increased. Although anyincrease can be implemented based on the application, in one embodimentthe increment is about 10% of the bit rate then being used.

Because network bandwidth varies over time, sudden drops in availablebandwidth may take place frequently. In such cases, the TCP stacktransmit rate will go down and the occupancy of the intermediate bufferwill increase. If this occurs for a long enough period, the free spacein the buffer will decrease so that the 90% watermark may be breached.In response, the broadcaster reduces the encoder's bit rate by a smallpercentage, for example about 15% of the bit rate then being used. Ifthis network problem is a temporary one, the TCP stack will again beable to send the backlog of data in the buffer so that the amount offree space in the buffer will rises again above the 90% mark. Theencoder's bit rate can then be increased.

On the other hand, if the network problem persists, the amount of freespace will continue to decline. Over a period of time, the buffer willfill and the other watermarks will be breached. As each watermark isbreached, the encoder's bit rate is further reduced. In one embodiment,these subsequent reductions may be larger (e.g., 33%, 50%, 50% for eachwatermark, respectively).

As described, the system intelligently exploits TCP stack behavior toestimate network status and reacts to provide optimal user experience inpresence of bandwidth variations. This may offer improved performance ascompared to using client-server interaction, which can be complicated,react more slowly, and may not make correct decisions if the encoder'soutput bit rate is expected to vary.

Fast-start Streaming

Conventionally, when a streaming media player receives a command to playa media stream, the media player fills its audio/video buffers beforestarting the playback. A buffer of five seconds or longer is typicallymaintained to ensure smooth playback of the media, since the time takento transfer the media stream over a network typically varies while themedia stream is meant to be played at a constant rate. Once the requiredamount of data is accumulated to fill the buffer sufficiently, the mediaplayer starts playing the requested content at normal play speed (i.e.,1.0×). Disadvantageously, the user must wait the amount of time requiredto fill the buffer before viewing the requested content. This time maybe very small in applications that send the stream faster than real time(e.g., a media stream from a storage device), but it is noticeable whenthe received media stream is at normal playback speed (i.e., 1.0×). Insuch a case, filling a five-second buffer would take five seconds(assuming no network communication issues). While this delay may betolerated in some streaming media applications, it becomes unbearablewhere the media streams are changing, such as in a personal mediabroadcaster in which the viewer is changing channels. In such a case,the user would have to wait for the buffer to refill each time thechannel (and thus the media stream) is changed.

To avoid this disadvantage, in one embodiment of the invention, themedia player performs a fast start when a new media stream is selected.With the fast start, the media player client application plays the videoimmediately as it is received from the media broadcaster while stillfilling its buffer. In this way, the user does not have to wait for themedia player's A/V buffers to fill up, e.g., upon channels changes, andthe media player can still build its buffers to provide smooth playback.The media player is able to fill its buffers even though it plays themedia stream immediately because the media player plays the A/V streamslightly slower than normal play speed. By playing the stream slightlyslower than normal playback speed, the part of the received media streamthat runs ahead of the stream played back is added to the buffer,resulting in accumulation of the A/V buffer—albeit more slowly. Becausethe user need not wait for content to be buffered and can immediatelystart watching the content, the experience is much more similar to thatwith a normal television.

In one example, the media player begins in fast-start mode playing backa received media stream immediately but at slightly slower speed thannormal play speed, e.g., 0.85× speed. Since the broadcaster is streamingat normal speed, the media player slowly accumulates media stream datain its A/V buffer. For example, if the playback speed is 85% normal, thedata accumulates in the A/V buffer at a rate of 15% (or 1.5 second forevery 10 seconds of received streaming data). Once the media player'sbuffer is full or otherwise reaches an acceptable level, the mediaplayer begins to play the media stream at a normal rate, and the A/Vbuffer stops accumulating data.

When the play speed of stream is changed slightly, the change in thevideo stream is generally not noticeable. However, the change in audiobecomes immediately perceptible. To take care of this, the media playermay use time-stretching on the audio stream while maintaining the“pitch” in the audio stream. One software tool that can be used totime-stretch the audio stream is SoundTouch, an open-source audioprocessing library. In one embodiment, the playback speed is increasedgradually from the low threshold (e.g., 0.85×) to the real time playbackspeed (e.g., 1.0×). The rate at which the playback speed is increasedmay be a function of the buffer level, so the user does not perceive anydrastic change in the playback speed. The timestamps of the audio andvideo samples may be changed according to the existing playback speed toreduce jerks in the video stream. As a result, the change in the audiostream is also not perceptible, and the user is less likely to perceivethe difference between the normal streaming speed and the initialfast-start playback speed.

Control Mode for Low Latency

One of the most used features in TV viewing is channel control, andusers expect such control operations to take at most one second toexecute. But streaming video over IP networks performs best when somedelay is added between the server and the client. This delay is neededto fill the A/V buffers in the media player client. The two requirementsof low delay for user interactions and smooth audio-video display areconflicting in nature. To deal with both of these requirements, in oneembodiment of the invention, two modes of operations are introduced:normal mode and control mode.

In the normal mode, the system performs conventional audio-videostreaming, wherein a buffer of five or more seconds is maintained by themedia player to ensure smooth playback. In this mode, the mediabroadcaster may also start buffering data if the network bit rate dropsbelow encoder bit rate (i.e., the encoder at the broadcaster runs aheadof the media stream transmission). The total delay between video inputto the media broadcaster and its viewing on the media player is thus thesum of three parameters: the time taken to buffer on the mediabroadcaster, the network transmission time taken for the stream to movefrom the media broadcaster to the media player, and the time taken tobuffer on the media player. The network transmission time taken for thestream to move from the media broadcaster to the media player cannot bedirectly controlled; however, both the media broadcaster and the mediaplayer can minimize delays caused by their buffers.

The system enters control mode when the user starts interacting with themedia broadcaster by way of the media player. In one embodiment, userinteraction is defined as when the user requests an IR command or tunercommand to control the operation of the A/V source device through themedia player user interface. In one embodiment, the system returns tonormal mode from control mode after a predetermined amount of time haspassed since the last action that could cause the system to startcontrol mode. In another embodiment, the system returns to normal modeimmediately after it performs the operations associated with going intocontrol mode, as described below.

On entering control mode, the media player and the media broadcasterchange their behavior relative to that in normal mode in a number ofways.

As mentioned, in the normal mode the media player performs normal A/Vstreaming wherein the media player reads the media stream from thenetwork buffer, parses the stream, and fills its audio/video buffers.This buffer is maintained to ensure smooth playback. When going intocontrol mode, the media player flushes the data that is present in theA/V buffers and the network buffer. In one embodiment, when going intocontrol mode, the media player makes the source filter flush all thedata buffered in the A/V buffers and also in all the filters downstream(decoders and renderers), which may be holding 2-3 seconds worth ofcontent. SP then flushes all the data present in the network buffer.Thereafter, the media player sends a notification to the mediabroadcaster to go into control mode and waits for the next I-framereceived from the media broadcaster.

After the flush operation on the source filter and the network buffer,discontinuities occur in the media stream. The filter has intelligencebuilt in so that if there is any packet discontinuity in the mediastream, the filter waits for the next I-frame. Any incoming data that isnot an I-frame is discarded by the source filter until a valid I-frameis detected. When the media broadcaster goes into control mode, it sendsan I-frame immediately. As soon as this I-frame is detected by thesource filter, it is sent downstream for rendering. While the mediaplayer remains in control mode, no buffering occurs in the sourcefilter; the samples are sent downstream for rendering as soon as theyare read from the network buffer. In this manner, the media playerreduces the latency on the client side.

In one embodiment, upon a change into control mode, the mediabroadcaster stops buffering data and flushes data currently contained inits buffers. The media broadcaster then immediately generates an I-frame(also known as key frame) to send to the media player. The I-frameallows the media player to reconstruct an image, whereas other types offrames that encode the frame based on previous frames would not allowthe media player to reconstruct the frame due to the discontinuity inthe media stream.

Given the dependency of modern audio-video encoding standards, however,it may not be desirable for the media broadcaster to stop buffering datacompletely. This is because without buffering there maybe too much dataloss, leading to an extremely poor user experience. A compromise cantherefore be made to balance low delay and a reasonable user experience.Based on a set of empirical values for achieving a good balance, anamount of data is allowed to be buffered by the media broadcaster duringcontrol mode as a function of bit rate of content. For example, incontrol mode, buffered data can be reduced by flushing the data if itcrosses a limit of about one second; however, other empirical values maybe used for various applications.

In one embodiment, the media broadcaster keeps track of effectivetransmission bit rate, for example by periodically calculating theaverage transmission bit rate for the last few seconds. Based on the bitrate it calculates permissible buffer usage. If usage goes beyond thecurrent limit then all data is removed and an I-frame is forced. Thisalso means encoder output rate is more than network transmission rate;therefore, encoder output is reduced to half of observed transmissionrate. Due to the resulting discontinuity in the media stream, an I-frameis also forced.

Too many user control commands in quick succession will force manyI-frames, which will adversely affect the encoder. Therefore, all bufferflushes and forcing of I-frames are preferably timed and spaced out byat least one second.

When returning to normal mode from control mode, the source filter ofthe media player pauses the playback, buffers (e.g., up to five or moreseconds) content in the A/V buffers, and then sends the data downstreamfor rendering.

To operate effectively in a low latency, low buffer environment, acommand can be immediately sent to the personal broadcaster to reducethe bit rate when in control mode. Without any additional adjustments,this would result in a reduction in image quality; however, because themenu screens being navigated typically feature very little motion, theframe rate of the video can be significantly reduced. With less framesto process, the personal broadcaster can output a stream with imagequality good enough to effectively read the on-screen text.

The low latency achieved by the dual mode operation of this embodimentis a very desirable characteristic for systems in which the usersinteracts with the media broadcaster through the media player. Theaddition of a control mode achieves this low latency, while the returnto normal mode once user interaction has stopped achieves the smoothstreaming desired for normal viewing. Moreover, in combination with thefast-start streaming described above, the control mode function providesa low latency control interaction experience for the user with aseamless transition from control mode to normal viewing.

Trick Play of Received IP Stream

In one embodiment, a user viewing a live stream being encoded in realtime by the personal broadcaster and displayed on the media player canreplay the last several seconds or minutes of content just viewed, or itcan pause the live stream for resumption at some point in the nearfuture. The personal broadcaster receives and processes the analog inputsignal; converts it into digital format; encodes the video in acompression algorithm such as MPEG-4, H.264, Windows Media Video Series9, or another appropriate format; and then streams the encoded viastream over TCP/IP (or an alternative protocol, such as UDP, RTP, RTSP)to the media player.

To enable this functionality, the media player caches the last fiveminutes (or some other fixed period of time as chosen by user or limitedby product manufacturer) of the audio and video content to a localstorage medium while receiving a video stream. The media player maystore the data on a local storage medium, such as a hard drive in thecase of a PC, or some removable media, including but not limited tocompact flash, smart media, a memory stick, or a micro drive.

When the user wishes to pause or replay the content, the user instructsthe media player to do so by selecting an appropriate labeled button inthe media player user interface. When the user instructs the mediaplayer to rewind, the media player accesses the content cached in itsstorage, allowing the user to scan through it, and play as desired. Oncethe user has “rewound” content, the user can then “fast forward” theviewing of the stream at faster than real-time speed until thecurrent-most point in the video stream is being displayed. When the userinstructs the media player to pause, the media player pauses the videostream being displayed but continues to receive the incoming stream,which it caches to its local storage medium. The media player continuesto cache the stream as it is received, until the point when the maximumnumber of minutes (or size of data) allowed to be cached when in pausemode is reached. If the maximum number of minutes (or size of data) isreached, the media player resumes playback. Otherwise, the media playerresumes playback when the user instructs the media player to do so.

Capturing, Editing, and Sending Video Clips from a Streaming Source

Embodiments of the invention also allow people to send video clips tofriends and acquaintances. In accordance with one embodiment, the mediaplayer device continually captures and caches the last five minutes (orsome other designated time period) of video and audio received. Themedia player automatically discards the earliest recorded content whenthe cached stream hits five minutes (or some other designated timeperiod), so that the five minutes being cached is always the five mostrecent minutes of media streamed.

When a user sees something of interest that the user would like tocapture and save or share, the user clicks on or selects a designatedbutton or command using the media player's graphical interface. Onceselected, the media player brings up a simple video editing interface,which enables the user to select the beginning and end of the clip thatthe user would like to capture. Once the bounds of the clip have beenselected, the user selects a command to save the clip or send the clipto another person.

In response to a command to send the captured video clip, the mediaplayer calls the email client resident on the user's client device,creates a new message, and attaches the video clip to the message. Theuser can then select the intended recipients of the message and send themessage. The address book databases can be those available from emailclients such as Microsoft Outlook, Lotus Notes, and others, as well asany Internet based messaging services, such as MSN Messenger and AOLInstant Messenger.

Personal Video Recorder (PVR) Functionality for Mobile Devices

As users get more accustomed to video experiences on mobile devices, andmobile storage solutions (e.g., removable flash media and small harddisk drives) become more robust and inexpensive, the desire to addpersonal video recorder functionality to these devices will emerge. Oneembodiment of the present invention adds the functionality of a personalvideo recorder to a mobile phone, communicator, PDA or other deviceconnecting to a Wide Area Network or other remote network outside auser's local area network.

One variation that accomplishes this can feature a scheduler as part ofthe remote client application which coordinates with an electronicprogramming guide. When the user launches the remote client application,he can search for and select the shows he would like to have recorded tohis remote client. When the time for the scheduled recording occurs, theremote client application initiates a recording. The application cancall the connection manager on the remote client, which in turn opens anInternet connection. The remote client application then connects to thepersonal broadcaster at the user's home.

Next, the remote client application can issue the right set of commandsrelated to channel selection and encoder settings on the server, andbegins to capture the incoming stream onto the local storage medium(e.g., hard disk drive or flash memory). This can happen in thebackground, so a user can be on phone call or listening to music(depending on other capabilities of the device) while the remote clientis recording.

If the recording is interrupted because a network connection is lost,the live streaming content can be temporarily stored on the local(built-in or removable) storage that exists in one variation of thepersonal broadcaster. Once a connection between the personal broadcasterand the remote client is reestablished, the content resumes the streamfrom the personal broadcaster to the remote client, taking intoconsideration the point at which the previously interrupted transferleft off. In another variation, an on-network storage device, such as aPC, can be used to store content temporarily after a connection betweenthe personal broadcaster and the remote client has been interrupted. Inanother embodiment, an entire show or media program is encoded andstored on the personal broadcaster (or in a storage device), and thentransferred to the mobile device in the background. Beneficially, thetransfer can be performed at a more efficient time for datatransfer—e.g., the file downloaded to a cellular phone overnight duringnon peak hours so that the content is available to the user for offlineviewing the following day.

In the case where the original source of the media being streamed is anon-network storage device (using the personal broadcaster as atranscoder/transrater), transfers between the personal broadcaster andthe remote client can be accomplished over time. That is, if a remoteclient loses network connectivity, the download pick ups and continueslater at the proper spot in the content.

Another embodiment enabling a PVR on a remote device, a variation of theembodiment described above, allows the personal broadcaster to work withan on-network storage device (such as a PC or a NAS or SAN device) toprovide for the user a PVR that can be accessed remotely. The personalbroadcaster takes in the analog content, digitizes and encodes thecontent, and then streams the resulting media stream to the on-networkstorage device for storage. When a user wants to access the content froma remote client, the personal broadcaster acts as an arbiter between theremote client, which wants to view the content, and the on-networkstorage device. The personal broadcaster receives the stream from theon-network storage device and transcodes or transrates the content ifnecessary before repackaging and streaming it to the remote client.

Pairing Programming being Viewed with Context-SpecificContent/Advertisements

One embodiment of the invention provides the ability for the client topresent the user with Web pages, scrolling text with news, or otherinformation that varies based on the content the user is currentlyviewing. For example, if the user is currently watching a San FranciscoGiants baseball game, the user can be presented with a “news ticker”that details other baseball scores around the league, or perhaps a Webpage with statistics and facts about the San Francisco Giants. Thecontent can be embedded in the interface of the client applicationitself or can be presented through the launching of another application,such as a Web browser. Similarly, the user can be presented with contentand context-specific advertisements. An example in the context of thesame baseball game would be an advertisement from the San FranciscoGiants ticket office, which hopes to attract viewers to purchase ticketsto a future game.

The broadcasting system can determine the content currently being viewedby the user in a number of ways. In one embodiment, the personalbroadcaster or client sends information, including the current time, thechannel lineup being used (e.g., location and cable TV provider), andthe current channel being tuned to, to the central server. The centralserver then takes the information received and examines the electronicprogramming guide applicable to the user's service. From information itis determined which show the user is currently viewing. Alternatively,the client can perform the programming guide lookup itself and transmitthis information to the central server.

After determining what show the user is currently viewing, overlaidinformation and/or advertisements can be transmitted from the centralserver or other server on the public Internet to the client mediaplayer. Alternatively, applications, such as a Web browser, can belaunched, simply sending the user to a specified URL. The client canalso contain the information necessary to queue any relevant informationor advertisement for display to the user. For example, the client canhave stored in its memory certain advertising banners or URLs ofrelevant Web sites that are queued depending on what type of content theuser views. This method alleviates much of the need for transmission ofcontent and or advertisements from a central server or other remoteserver.

Embodiments that include personal video recorder functionality (usinglocal storage on the personal broadcaster or using storage of theon-network storage device) can provide for context-specific ads andinformation even when playing a previously recorded show. When recorded,the content is “tagged” with information indicating the programmingbeing captured. On play back, this information can be used to promptcontent specific information and ads.

Content-specific Edge Preserving Pre-filter

Low bit rate coding involving block based video coders produce strongblocking artifacts. To reduce the severity of these artifacts, in oneembodiment of the invention, pre-filtering is employed to simplify theimage content before compression. The pre-filters often comprise lowpass filters, which not only smooth blocking artifacts but alsoundesirably reduce image details. Moreover, low pass filters are notadaptive to video content, which makes them ill-suited for perceptualvideo encoding. To avoid the limitations of previous pre-filters, oneembodiment of media player performs a content-specific edge estimationalgorithm on the media stream received from the media broadcaster. Inaccordance with this embodiment, an edge estimate gives the location ofthe details in the image that should be preserved while a motionestimate gives a classification of whether the content is in high,medium, or low motion.

In one embodiment, the media player applies a pre-filter on the receivedstream. The pre-filter comprises a low pass filter having pass bandcharacteristics that are changed based on an edge estimate, a motionlevel estimate, and an encoding bit rate. Based on the motion levelestimate and the encoding bit rate, a filter characteristic is definedfor a frame. The filter characteristic is then fine tuned at the pixellevel based on the edge estimate. Using this approach, a higher degreeof smoothing is used for high motion contents and lower degree for lowmotion content, while leaving the details intact.

In one embodiment, two sets of adaptive low pass filters are defined.For low bit rate encoding, the following Gaussian filter of size 5×5 isused:

${G( {x,y} )} = {\frac{1}{2}\;\pi\;\sigma^{2}\;{{\exp( {- \frac{( {x^{2} + y^{2}} )}{2\;\sigma^{2}}} )}.}}$For high bit rate encoding, a low pass filter having an average mask ofsize 3×3 is used, as shown in the table below.

$\begin{matrix}1 & 1 & 1 \\1 & \psi & 1 \\1 & 1 & 1\end{matrix}\quad$The parameters σ and ψ are varied based on the edge estimate, motionlevel estimate, and the encoding bit rate. Increasing σ or decreasing ψincreases the smoothness of the video, while the opposite decreases thesmoothness of the video. The edge estimate,

, is operated at pixel level and is obtained by taking the gradient atall eight directions. This is given by:

=ΣΔf _(θ), θ{0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°},where Δf_(0°)={(x,y)−(x+1,y)}, Δf_(45°)={(x,y)−(x,y+1)}, . . . .

If

is greater than a threshold T, no pre-filtering is performed on thecurrent pixel, thereby preserving the image details. The motion levelestimate gives a classification of whether the motion is high, medium,or low motion. The estimate is based on the bits required for thecurrent frame and the recursive average of the bits per frame. If thecurrent frame bits are greater than α (always >1) times the recursiveaverage, the current video content is declared as high motion, and ifthe current frame bits are less than β(<1) times the recursive average,the video content is classified as low motion. Otherwise, it isclassified as medium motion. Based on the type of motion, the filterstrength is varied. For high motion content, for example, a relativelyheavy smoothing filter can be applied as compared to low motion content.

This pre-filtering method not only retains the image details but also iscontent specific. That is, the filters are adapted to the motion type:high, medium, or low. This pre-filtering method provides non-blocky,constant quality encoded video for all motion types. Unlike conventionalpre-filters this reduces the frame drops without compromising quality.

Frame Rate Regulation and Quality Control for Encoder

Most video software encoders at low bit rates dynamically drop videoframes to meet some specific target bit rate, often during high motion.This dropping of frames can lead to jerky video and fluctuating qualitylevels. As potentially large sections of frames are dropped, the motionestimation process becomes ineffective. To avoid this problem, oneembodiment of the media broadcaster regulates frame rate using amulti-level approach designed to enhance the viewing experience of theuser by sustaining both frame rate and quality at each level.

In one embodiment, the encoder in the media broadcaster estimates asustainable frame rate based on a Sustainability measure, SM. Fourlevels of frame rate regulation are defined. Based on SM, the frame rateis selected and an appropriate quality level is defined. Each stage ofthe algorithm keeps the inter-frame distance constant, preservingtemporal video quality. This results in better motion estimation andacceptable spatial video quality levels.

Frame rate regulation is performed in one embodiment according to thefollowing algorithm. The target frame rate defined by the encoder is F₀.A sustainability measure, SM, determines whether the frame rate can besustained over the time interval T. SM can be defined as the ratio ofthe bit pool available to the estimated bits required for the next Tseconds. The bit estimate is a product of frames per T seconds with therecursive average of the bits per frame. The SM may be calculated basedon the “motion” estimate and the target bit rate. The “motion” estimateis based on the recursive average of the encoded bits per frame. In oneembodiment, the frame rates at subsequent levels are: F₁=F₀/2; F₂=F₀/3;and F₃=F₀/5.

If F_(i) denotes the assigned frame rate for level i, based on SM, adecision is made every T whether the encoder should continue in the samelevel or move to a level higher or a level lower. If SM is less than a(indicating that that the current frame rate, F_(i), cannot be sustainedfor the time interval T), the encoder moves to level i+1. If the encoderis already at the lowest frame rate, F₃, it stays there. This operationis again performed after every T. The level thus goes down when bit rateis not sufficient enough to cater high motion content bit rate need.

While in level i, as long as i is not 0, SM for level i−1 is checkedafter time interval of T. If the SM is greater than β (>1), it indicatesthat the current content can be encoded at level i−1, so the encodermoves to level i−1. This method thus tries to maintain the inter-framedistances constant at each level thereby improving the overall videoquality.

Dynamic Parameter Control for Video Encoder

In a real time video streaming environment, network characteristicschange dynamically. To improve the use of the network resources, a videoencoder should be able to adapt to these network changes; however, mostof the standard video encoders do not support such adaptation. Inaccordance with one embodiment of the invention, a scheme for theWindows Media Video (WMV9) encoder is provided wherein the parameterscan be changed dynamically during streaming.

The following parameters can be changed dynamically while streaming isin progress: bit rate, frame rate, video smoothness, and I-frameinterval. The bit rate can adapt to the rate that can be supported bythe network at a given time, and rate control buffer delay, bits perframe, and quantization step size vary according to changes in bit rate.Frame rate depends on the dynamically changed bit rate. At lower bitrates, high frame rates cannot be sustained, which creates the need insome circumstances for a dynamic frame rate. The video smoothnessparameter indicates the encoded video quality. Lower bit ratessupporting high values of video smoothness can cause jerky video, whilelow values of video smoothness at higher bit rates leads to underutilization of the available resources. Depending on the videosmoothness parameter, the quantization upper bound and lower bound stepvalues are changed, which affects the quality of the video. Because thebits required to encode I-frames are greater than bits required for Pframes, I-frame intervals are larger for lower bit rates. I-frameintervals can be reduced at higher bit rates, where more bits can beafforded.

Accordingly, the encoder in the media broadcaster can dynamically adjustthese parameters to adapt to the changing network characteristics andoptimize use of system resources. This allows for improved performancethan the standard WMV9 encoder, which does not dynamically change theabove parameters in a real time streaming environment. Althoughdescribed in the context of video encoding with Windows Media Video(WMV9), this method can be applied to other video compression formats,including MPEG-4, H.263, H.264, and any other compression formats thatuse the same or similar parameters mentioned herein.

Point and Click Interaction with Traditional CE Menus

Because the personal broadcaster digitizes, encodes and streams theanalog output of the A/V source devices being used, the client presentsthe user with the full interface of the A/V source device. The defaultparadigm for navigating menus of the A/V source device that are renderedby the client is exactly the same as it would be for a user viewing theA/V source device in a more traditional fashion. That is, the mode ofnavigation typically involves “Up,” “Down,” “Right,” “Left,” and“Select” as its key components. However, alternative methods forinteracting with menus and other lists are possible. For example,instead of pressing the “Down” command four times to highlight an itemfour spaces down from what is currently highlighted, an embodiment ofthe media player allows a user simply to point and click directly on thedesired menu item. This speeds up the interaction and takes advantage ofthe rich human interface tools (e.g., keyboard and mouse) that areavailable in many computing devices but not generally used withtelevisions.

Hot Spot Finder

In one embodiment of the invention, the media player includes adirectory of hotspots (wireless broadband networks available in publiclocations) stored on the client device and accessible when the client isnot connected to a network. Such a directory allows the user more easilyto find a location where the user can gain access to the personal mediabroadcaster.

Testing and Configuring a User's NAT

For users that have a home Internet gateway that includes a NetworkAddress Translation (NAT), some configuration can be required to allow auser to access the personal broadcaster from a remote network. This isbecause incoming requests are rejected by many NATs unless the NAT hasbeen explicitly instructed how to forward the incoming packets. Thereare many methods for solving this problem, some more desirable andautomated than others. Some embodiments of the invention include amulti-step process for determining and implementing the possiblesolutions.

The system may first attempt to determine whether the home Internetgateway supports UPnP (Universal Plug 'N Play). If so, the personalbroadcaster may be able to control the home Internet gateway using UPnP.The personal broadcaster can thus instruct the NAT to forward aspecified port to the internal IP address dedicated to the personalbroadcaster.

If the home Internet gateway does not support UPnP, the system may thenattempt to determine the type of NAT in the home Internet gateway, andspecifically whether the NAT is a full cone NAT. This detection may beperformed by using the central server as a STUN server, which runsvarious tests to determine what the type of the NAT behind which thepersonal broadcaster sits. There are four basic types of NATs: fullcone, restricted cone, port restricted cone, and symmetric. A full coneNAT is a NAT that allows a client behind it to receive messages from oneexternal machine that are addressed to an IP address and port that theinternal client used in sending a message to another external machine.If the personal broadcaster sits behind a full cone NAT, the followingis possible: The personal broadcaster from time to time sends a messageto the central server, and the central server makes a note of the IPaddress and port from which it was received. When a remote client wishesto connect to the personal broadcaster, it asks the central server forthe address and port recently used by the personal broadcaster to sendits message. The remote client can use the same IP address and port tolocate and connect to the personal broadcaster. If the NAT is not a fullcone NAT, another method is used.

A third possible method to use comprises a UDP “hole punching”technique. This technique, which is known to those of ordinary skill inthe relevant art, would involve using the central sever as a way to“introduce” the remote client and the personal broadcaster. The methodworks for all NAT types except for symmetric NATs (so the STUN testwould be useful for determining if this is a viable option) and uses thecentral server to cause both devices to send messages to one anothersimultaneously. Because both devices believe they are “initiating” theconversation, the return packets are permitted to flow through the NATto the destination device.

If none of the above or other methods are viable solutions, the presentinvention can walk the user through the steps for manual configurationof the NAT on the home Internet gateway. To make this easy andintegrated into the set up process for the personal broadcaster, theconfiguration screens for the home Internet gateway can be embedded inthe window that houses the set up application. This provides the userwith a greater sense of seamlessness.

On-device EPG

One variation of the present invention features an electronicprogramming guide (EPG) that resides locally on a client. The EPG isconfigured at initial configuration of the personal broadcaster. Theuser is asked for a zip code and the service and package to which theuser subscribes. Based on this information, the client applicationdownloads an EPG that covers the next several days. From time to time,the EPG is updated via download from the central server or anotherserver from a third party provider. The EPG can be stored locally on theclient.

Beneficially, the EPG can be made interactive. Among the many featuresenabled by an on-device EPG, a user could search and sort programmingcontent by a number of variables, and a single “click” on a channel canautomatically tune the A/V source device and media player to the desiredchannel.

Community or “Buddy” List

One embodiment of the media player incorporates a “buddy list.” Usingthe buddy list, a user can connect to personal broadcasters that resideat different locations. For example, if Charlie declares Amy as a“buddy,” Charlie's personal broadcaster appears on Amy's buddy list. Bychoosing Charlie's personal broadcaster, Amy connects to Charlie'sdevice. All of the necessary settings (e.g., IP address, port, password,and any other required settings) are automatically provided to thebuddy.

Last Come, Last Served

Another embodiment of the invention allows only a single client to beconnected to the personal broadcaster at any given time. The broadcastermay implement a number of priority schemes, one of which is last comelast served. In this scheme, if a client A is connected and client Battempts to connect, priority is given to the client B. One embodimentcan provide a message to client A informing the user of client A thatthe client is about to be disconnected. The user of client A may beprovided the opportunity to override this rule and remain connected.This priority system is especially useful in the situation where aperson logs in at home, then leaves the house without disconnecting andattempts to log in from a remote client.

Encryption and Security

Various known security mechanisms can be used in different embodimentsof the present invention. Example of security mechanisms that can beused with the personal media broadcasting system described hereininclude, but are not limited to, password protection, communication overa secure link, encrypting the content sent over the remote network.

Blocking Out the Local Display

In another embodiment the media broadcaster includes A/V pass-throughsfor all of the inputs, where there is an output that corresponds to eachof the inputs. This saves the user from using multiple outputs on an A/Vsource device and may provide a complete method for prohibiting twosessions. Moreover, this embodiment can be used to prohibit thesimultaneous occurrence of a client connection to a personal broadcasterand a local viewing of the A/V source which is plugged into the personalbroadcaster. For example, if someone were watching a pay per view movieat home, and a user connected to the personal broadcaster tunes into thesame movie, the personal broadcaster can disable its A/V outputs.Whether the A/V outputs are disabled can depend on the content. Forexample, in one embodiment only pay per view content triggers ablocking, whereas regular programming does not. This discriminationscheme can be integrated with an EPG, as discussed above.

Summary

The foregoing description of the embodiments of the invention has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the aboveteachings. It is therefore intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto.

1. A personal media broadcaster comprising: an input interface forreceiving an audio/video signal from one or more audio/video sourcedevices; a processor coupled to the input interface and configured toconstruct a media stream suitable for transmission over a network fromthe audio/video signal; a buffer coupled to receive the media stream,the buffer coupled to the processor for communicating an amount of freespace remaining in the buffer, wherein the processor constructs themedia stream by encoding the audio/video signal using a bit rateselected at least in part based on the amount of free space remaining inthe buffer; and a network interface for transmitting the media streamstored in the buffer to a client over a network.
 2. The personal mediabroadcaster of claim 1, wherein the processor is configured to increasethe bit rate for encoding the audio/video signal if the amount of freespace remaining in the buffer remains above a predetermined watermarkfor a predetermined amount of time.
 3. The personal media broadcaster ofclaim 2, wherein the bit rate is increased by about 10% if the amount offree space remaining in the buffer remains above a predeterminedwatermark for a predetermined amount of time.
 4. The personal mediabroadcaster of claim 1, wherein the processor is configured to decreasethe bit rate for encoding the audio/video signal if the amount of freespace remaining in the buffer decreases below a predetermined watermark.5. The personal media broadcaster of claim 4, wherein the bit rate isdecreased by about 15% if the amount of free space remaining in thebuffer decreases below a predetermined watermark.
 6. The personal mediabroadcaster of claim 4, wherein the processor is configured to increasethe bit rate for encoding the audio/video signal, after having decreasedthe bit rate, if the amount of free space remaining in the bufferincreases above the predetermined watermark.
 7. The personal mediabroadcaster of claim 1, wherein a plurality of watermarks are predefinedfor the buffer, each watermark indicating an amount of free spaceremaining in the buffer, and wherein the processor is configured todecrease the bit rate for encoding the audio/video signal each time theamount of free space remaining in the buffer decreases below one of thewatermarks.
 8. The personal media broadcaster of claim 7, wherein theprocessor is configured to increase the bit rate for encoding theaudio/video signal each time the amount of free space remaining in thebuffer increases above one of the watermarks.
 9. A personal mediabroadcasting system comprising: a personal media broadcaster having aninput interface for communication with one or more audio/video sourcedevices, the personal media broadcaster configured to construct a mediastream suitable for transmission over a network from a signal receivedfrom one of the audio/video source devices, the media stream constructedby encoding the signal using a bit rate selected at least in part basedon an amount of free space remaining in an intermediate output buffer,the personal media broadcaster further including a network interface fortransmitting the media stream from the intermediate output buffer; and aclient module for communicating with the personal media broadcaster overa network connection to receive the media stream, the client moduleconfigured to play the media stream for a user.
 10. The system of claim9, wherein the personal media broadcaster increases the bit rate forencoding the signal if the amount of free space remaining in theintermediate output buffer remains above a predetermined watermark for apredetermined amount of time.
 11. The system of claim 9, wherein thepersonal media broadcaster decreases the bit rate for encoding thesignal if the amount of free space remaining in the intermediate outputbuffer decreases below a predetermined watermark.
 12. The system ofclaim 11, wherein the personal media broadcaster increases the bit ratefor encoding the signal, after having decreased the bit rate, if theamount of free space remaining in the intermediate output bufferincreases above the predetermined watermark.
 13. The system of claim 11,wherein a plurality of watermarks are predefined for the intermediateoutput buffer, each watermark indicating an amount of free spaceremaining in the buffer, and wherein the personal media broadcasterdecreases the bit rate for encoding the signal each time the amount offree space remaining in the intermediate output buffer decreases belowone of the watermarks.
 14. The system of claim 13, wherein the personalmedia broadcaster increases the bit rate for encoding the signal eachtime the amount of free space remaining in the intermediate outputbuffer increases above one of the watermarks.
 15. A method for providingaccess to an audio/visual source at a location remote from theaudio/visual source, the method comprising: receiving an input signalfrom an audio/visual source device; constructing a media stream suitablefor transmission over a network by encoding the input signal using a bitrate selected at least in part based on an amount of free spaceremaining in a buffer; storing the media stream in the buffer; andsending the media stream from the buffer to a remote client over anetwork.
 16. The method of claim 15, further comprising: increasing thebit rate for encoding the input signal if the amount of free spaceremaining in the buffer remains above a predetermined watermark for apredetermined amount of time.
 17. The method of claim 15, furthercomprising: decreasing the bit rate for encoding the input signal if theamount of free space remaining in the buffer decreases below apredetermined watermark.
 18. The method of claim 17, further comprising:after decreasing the bit rate for encoding the input signal, increasingthe bit rate if the amount of free space remaining in the bufferincreases above the predetermined watermark.
 19. The method of claim 15,wherein a plurality of watermarks are predefined for the buffer, eachwatermark indicating an amount of free space remaining in the buffer,the method further comprising: decreasing the bit rate for encoding theinput signal each time the amount of free space remaining in the bufferdecreases below one of the watermarks.
 20. The method of claim 19,further comprising: increasing the bit rate for encoding the inputsignal each time the amount of free space remaining in the bufferincreases above one of the watermarks.
 21. A method for providing accessto a video source at a location remote from the video source, the methodcomprising: receiving a video signal; creating a media stream from thevideo signal, the media stream encoded using a bit rate selected atleast in part based on an amount of free space remaining in an outputbuffer; storing the encoded media stream in the output buffer; andsending the media stream from the output buffer to a remote client overa network.
 22. A method for streaming a media signal to a remotesubscriber location, the method comprising: receiving a media signal fortransmission to a subscriber location; constructing a media streamsuitable for transmission over a transmission network by encoding thereceived media signal using a bit rate selected at least in part basedon an amount of free space remaining in an output buffer; storing themedia stream in the output buffer; and transmitting the media streamfrom the output buffer to the remote subscriber location over atransmission network.
 23. The method of claim 22, further comprising:increasing the bit rate for encoding the input signal if the amount offree space remaining in the output buffer remains above a predeterminedwatermark for a predetermined amount of time.
 24. The method of claim22, further comprising: decreasing the bit rate for encoding the inputsignal if the amount of free space remaining in the output bufferdecreases below a predetermined watermark.
 25. The method of claim 24,further comprising: after decreasing the bit rate for encoding the inputsignal, increasing the bit rate if the amount of free space remaining inthe output buffer increases above the predetermined watermark.
 26. Themethod of claim 22, wherein a plurality of watermarks are predefined forthe output buffer, each watermark indicating an amount of free spaceremaining in the output buffer, the method further comprising:decreasing the bit rate for encoding the input signal each time theamount of free space remaining in the output buffer decreases below oneof the watermarks.
 27. The method of claim 26, further comprising:increasing the bit rate for encoding the input signal each time theamount of free space remaining in the output buffer increases above oneof the watermarks.
 28. The personal media broadcaster of claim 1,further comprising a decoder coupled to the input interface forreceiving the audio/video signal from the one or more audio/video sourcedevices via the input interface and for decoding the audio/visualsignal, wherein the processor is coupled to the input interface via thedecoder.
 29. The method of claim 15, further comprising decoding theinput signal.
 30. A device comprising: an input interface configured toreceive an audio/video signal; a processor coupled to the inputinterface and configured to encode the audio/video signal using a bitrate; a buffer configured to receive the media stream, wherein the bitrate is selected at least in part based on an amount of free spaceremaining in the buffer; and an output interface configured to transmitthe media stream stored in the buffer.
 31. The device of claim 30,wherein the processor is configured to increase the bit rate forencoding the audio/video signal if the amount of free space remaining inthe buffer remains above a predetermined watermark for a predeterminedamount of time.
 32. The device of claim 30, wherein a plurality ofwatermarks are predefined for the buffer, each watermark indicating anamount of free space remaining in the buffer, and wherein the processoris configured to decrease the bit rate for encoding the audio/videosignal each time the amount of free space remaining in the bufferdecreases below one of the watermarks.
 33. The device of claim 32,wherein the processor is configured to increase the bit rate forencoding the audio/video signal each time the amount of free spaceremaining in the buffer increases above one of the watermarks.
 34. Thedevice of claim 30 wherein the buffer is configured to receive the mediastream prior to transmission by the output interface.